What the “Skeptics” of Climate Catastrophe are Skeptical Of: Nordhaus Reconsidered
The most frustrating thing about being a scientist skeptical of catastrophic global warming is that the other side is continually distorting what I am skeptical of.
In his immodestly titled New York Review of Books article “Why the Global Warming Skeptics Are Wrong,” economist William Nordhaus presents six questions that the legitimacy of global warming skepticism allegedly rests on.
- Is the planet in fact warming?
- Are human influences an important contributor to warming?
- Is carbon dioxide a pollutant?
- Are we seeing a regime of fear for skeptical climate scientists?
- Are the views of mainstream climate scientists driven primarily by the desire for financial gain?
- Is it true that more carbon dioxide and additional warming will be beneficial?
Since the answers to these questions are allegedly yes, yes, yes and no, no, no, it’s case closed, says Nordhaus.
Except that he is attacking a straw man. Scientists (or non-scientists) who are “skeptics” are skeptical of catastrophic global warming—not warming or human-caused warming as such. So much for 1 and 2. We refuse to label CO2 a “pollutant” because it is essential to life and because we do not believe it has the claimed catastrophic impact. So much for 3. And since 4-6 don’t pertain to the scientific issue of catastrophic warming, so much for them, as well.
The object of our skepticism, catastrophic global warming, means warming caused by greenhouse gasses that would so dramatically heat up the earth that despite the proven climate adaptability of hydrocarbon-powered civilization (see “How Capitalism Makes Catastrophes Non-Catastrophic”), populations the world over would experience impoverishment, mass suffering, and death.
Why are we skeptical of this claim? Because there is radically insufficient evidence for it.
This may seem implausible, because the news media bombard us with stories of new studies, new findings, new models, new international summits allegedly confirming catastrophic global warming. But what these stories leave out is the evidential status of these developments—what any given study or model actually proves. And the answer is, little to nothing, because the present ability of scientists to understand, model, and predict the climate is far, far lower than we are led to believe.
To say that modeling the climate for long-term predictions is difficult given the current state of climate science is like saying that it would be difficult for your five-year-old son to build a 400 horsepower car from re-purposed Toys ‘R’ Us purchases. Imagine that he comes to you with pages and pages of plans he’s sketched out in crayon. The “car” will cost $22,827.35 worth of toys.
Why wouldn’t you reach for your credit card? Is that because you’re against teaching kids engineering? Is it because his sworn enemy, your daughter, is paying you off? Or perhaps it’s because this project is obviously beyond the capability of a five-year-old, and that his crayon schematics don’t offer convincing evidence that he is in fact the kind of once-in-a-generation prodigy who could somehow pull it off.
If one understands how monumental an undertaking it would be to produce a sound climate model, one can see that today’s climate modelers are making assertions no less implausible than our five-year old’s fantasy.
In physics it is generally possible to exactly predict the behavior of systems involving two independent bodies, whether planets interacting through gravity or elementary particles through the electromagnetic field. More bodies means no exact solution to the dynamical equations and a zoo of different approximations, usually requiring computational simulation, which takes more and more time as the number of bodies being simulated increases. Indeed the computation time generally grows exponentially with the number of bodies.
The global climate system comprises an astronomical number (at least billions) of effectively independent “bodies,” which is to say of isolatable, relatively uniform chunks of air, ocean, and earth. Their interactions span the complexity spectrum, from the mechanical push-and-pull of an ocean current to the lesser-known dynamics of cloud formation to intricate, biological mechanisms like plant growth and respiration that have evolved over billions of years.
Solving this kind of complex system is outside the realm of controlled approximations and reasonable estimates. It’s in the realm of random stabs, on any objective assessment of our current scientific powers. Since attempts to model this system are the basis of claims for catastrophic global warming, the evidence we need to consider pertains to whether or not such models are capturing enough of the detailed mess of forces that actually drives the climate.
Many different climate processes affect the energy balance between the earth and outer-space and thus affect temperatures on the Earth. One such process is the greenhouse effect, by which CO2 and other gases trap some extra solar energy in the atmosphere and convert it into heat. It is widely acknowledged that the CO2-linked greenhouse effect itself can produce only a modest warming going forward because the incremental warming produced by each extra liter of CO2 gets smaller and smaller as more CO2 is added.
The catastrophist projections are based on the idea that this modest warming will trigger an entirely separate set of feedback mechanisms that will multiply the warming many times. For instance warming is projected to increase ambient levels of water vapor, itself a greenhouse gas; melting ice will expose more earth or open water, which tend to absorb more solar energy as heat; temperature-linked changes in cloud patterns affect how much solar energy gets reflected back to space or back to the Earth.
There are also negative feedbacks, meaning processes that come into play due to warming, or to CO2 increases, that wind up counteracting that warming. Examples include enhanced re-radiation of energy back into space at higher temperatures, increased absorption of CO2 into the oceans, and increased quantities of organic matter capturing CO2. Indeed some supposedly positive feedbacks, like certain cloud effects, may turn out actually to be negative ones.
Moreover, nature does not simply provide us with a list of all the relevant feedbacks, or climate processes in general. There is no systematic procedure by which the set of processes included in current climate models are picked out from the catalogue of all possible such processes. The procedure is simply for modelers to engage their own imaginations, given our current knowledge, to conceive possible effects and gather evidence to confirm or falsify them.
How many known ones have been intentionally discarded due to a lack of knowledge and evidence about how to incorporate them? How many have just not been thought of to date?
In a certain sense, this is the nature of any scientific theory. But this is why such theories have to produce specific, detailed predictions, confirmed by observation, to show that they have captured the relevant causal factors. Apart from this, there is a lot of room here for the ultimate outcome of the models to be controlled by ideological predispositions—like that, of all the underlying drivers, the decisive one just happens to be CO2, the one with a clear link to the functioning of modern, industrial capitalism.
What would be a rational response when your five-year-old car enthusiast presents you with his crayon plans, protesting that he’s also proven his case by putting together a scale model in Legos? First you might point out that while his plans are impressive for a boy his age, it’s rarely the case that reality works out just like a priori plans and models suggest.
Rather than setting him loose at toysrus.com with your credit card, you might suggest he start off with a scaled-down project, like an RC kit. Then, if that’s a success, maybe an introduction to simple wood and then metal work. As he gets older and proves himself at each stage, he could move on to machine shop projects, welding, and an apprenticeship with a real car mechanic.
This kind of demonstrated, step-by-step progress is how legitimate inventions, and inventors, are made. At the end of the process, they no longer agitate for sizable investments on the basis of their original crayon plans.
And such demonstrated, step-by-step progress is exactly what a reasonable person ought to demand from the global warming catastrophists. Not mere simulations, generated by model code that they control and have played with for years. Since the odds are so small, a priori, that they have actually cracked the excruciatingly complicated problem of global climate prediction, we need dramatic positive evidence. Lesser evidence is powerless to overcome the overwhelming odds against being able to delicately sort out the mess of climate drivers and feedbacks.
The catastrophists need to demonstrate their methodology by applying it to smaller problems whose outcomes we don’t have to wait a century for. They need to derive unambiguous, detailed predictions for these outcomes and see them borne out. By “detailed” I mean predictions of not just a single number, like a cumulative warming trend, that could just be accidentally correct—and they’re not even getting predictions on these simpler metrics right. I mean predictions of a more intricate, unaccidental nature.
For instance, climate models predict a detailed pattern of warming that occurs at different rates in different parts of the globe and, importantly, at different altitudes in the atmosphere. But when we look in actual climate data for the specific, altitude-dependent warming signature produced by these models, we find something entirely different.
And that’s only half the problem. Before we can test models, we need this historical climate data to be accurate in order for the comparison to mean anything. Even for the one central climate variable, global average temperature, the reconstructed data is fraught with uncertainties and scientific misconduct.
What has always to be kept in mind on these issues, is (i) the massive complexity of the problem the catastrophist modelers are claiming to have solved relative to the current state of climate science, and (ii) what this implies about the onus of proof. Their claim is to have accomplished a scientific miracle with tools that by any reasonable analysis are far from capable of the task.
Absent shocking evidence of success on their part, the conclusion to draw is not: catastrophic global warming has just moderate odds of occurring. The conclusion is that these models bear as much relationship to reality as your son’s crayon plans bear to a real car. And suggestions about how to transform the entire world economy based on these models should be treated accordingly.
Eric Dennis, who holds a Ph.D. in physics from UC Santa Barbara, is a Senior Fellow at the Center for Industrial Progress.